This invention relates to reinforced polymers, more particularly to molded polyurethane and/or polyurea polymers which contain filler materials.
It is well known to employ various filler materials to modify the physical properties of polymeric materials. The use of such fillers is thoroughly described in, for example, Handbook of Fillers and Reinforcements for Plastics, Katz et al., eds., Van Nostrand Reinhold Company, New York (1978). Polyurethane and/or polyurea polymers having their physical properties modified by fillers are increasingly being used to replace metals. Of particular interest are certain automotive applications, especially automotive exterior body parts. Filled polymers offer several advantages in these applications. In particular, the parts are often better able to withstand minor impacts, such as are encountered in low speed collisions, without damage, and they may also exhibit decreased tendency to rust.
The filled polymers used in making these body parts preferably exhibit a demanding combination of physical properties. They should have good thermal properties over a wide temperature range, have good dimensional stability, be rigid enough to bear their own weight, be flexible-enough to withstand minor impacts without damage, and be relatively unaffected by extremes in weather conditions. Success in meeting most of the foregoing criteria has been achieved by using certain reinforced polymers.
However, when a filler is added to improve one or more physical properties, it also frequently undesirably affects other physical properties. For instance, some fillers added as reinforcing fillers to polyurethanes reduce the impact strength and/or diminish surface quality. Such effects are discussed, for instance, by Maik and Fisa in "Mica as a Reinforcement for Polyurethanes RIM", in Plastics Compounding, vol.9, no.3, May/June 1986, pp. 16-21. In that discussion it is noted that addition of certain glass flakes and mica fillers reduces the notched Izod Impact Strength of a polyurethane, from 3.45 to 3.89 for unfilled material to 1.76 to 1.96 for the same material containing about 20 percent by weight glass flake or certain phlogopite micas.
In spite of the lowering of impact strength observed when various mica fillers are used, certain micas have been suggested for use in polyurethanes. For instance, Japanese 62-54755 discloses mica having an average diameter of less than about 50 micrometers used in polyurethane in an amount of from about 5 to 25 percent by weight. Japanese 58/2011829 discloses the use of flake fillers, including certain micas having a thickness of about 3 to 15 micrometers and aspect ratios (diameter to thickness) of 20 to 200, in polyurethanes. Similarly, certain mica flakes having a flake diameter less than about 50 micrometers are used in polyurethanes, as described in Japanese 85/195600. In general, when mica is used in polyurethanes and/or polyureas, particularly reaction injection molded polyurethanes and/or polyureas, it significantly reduces the impact strength of the final product.
Filled polymers also often have relatively poor surface qualities in comparison with metals. Metals provide a characteristically mirror-like surface after painting. Unfilled polymers often approach or equal the surface qualities of metals, but reinforced or extended polymers usually are significantly inferior in this respect. Because surface appearance, particularly of a painted surface, is of major importance in some applications to the consumer, it is highly desirable to provide a polymeric material having improved surface qualities. Flaked glass is an example of a reinforcing filler which can give impact strengths satisfactory for some applications, but which frequently gives poor surface properties.
Similarly, there are other applications wherein both impact strength and excellent surface appearance in a filled polymer is desired. Accordingly, it would be desirable to provide a filled polyurethane and/or polyurea polymer having desirable surface qualities as well as high impact strength.